PVR Calculator
Calculate Pulmonary Vascular Resistance for assessment of pulmonary hypertension
Calculate Pulmonary Vascular Resistance
Normal: 10-20 mmHg
Normal: 6-12 mmHg
Normal: 4-8 L/min
PVR Results
Formula: PVR = 80 × (MPAP - LAP) / CO
TPG: 0.0 mmHg
Normal: < 240 dynes·sec·cm⁻⁵
Normal: < 3.0 Wood Units
Clinical Interpretation
Enter values to calculate PVR
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Clinical Context
Clinical Examples
Example 1: Pre-capillary Pulmonary Hypertension
Clinical scenario: 58-year-old with progressive dyspnea
MPAP: 35 mmHg (elevated)
PCWP: 10 mmHg (normal)
Cardiac Output: 4.5 L/min
Calculation & Interpretation
PVR = 80 × (35 - 10) / 4.5 = 444 dynes·sec·cm⁻⁵ (5.6 WU)
TPG = 35 - 10 = 25 mmHg (elevated)
📋 Diagnosis: Mild-moderate pre-capillary PH (WHO Group 1, 3, 4, or 5)
Example 2: Post-capillary Pulmonary Hypertension
Clinical scenario: 72-year-old with heart failure
MPAP: 38 mmHg (elevated)
PCWP: 22 mmHg (elevated)
Cardiac Output: 5.0 L/min
Calculation & Interpretation
PVR = 80 × (38 - 22) / 5.0 = 256 dynes·sec·cm⁻⁵ (3.2 WU)
TPG = 38 - 22 = 16 mmHg
📋 Diagnosis: Post-capillary PH due to left heart disease (WHO Group 2)
Example 3: Normal Hemodynamics
Clinical scenario: 45-year-old with dyspnea, evaluation for PH
MPAP: 18 mmHg (normal)
PCWP: 9 mmHg (normal)
Cardiac Output: 6.0 L/min
Calculation & Interpretation
PVR = 80 × (18 - 9) / 6.0 = 120 dynes·sec·cm⁻⁵ (1.5 WU)
TPG = 18 - 9 = 9 mmHg (normal)
✅ Diagnosis: Normal pulmonary hemodynamics - no PH
PVR Reference Ranges
Standard Units (dynes·sec·cm⁻⁵)
Wood Units (WU)
Unit Converter
Example:
• 240 dynes·sec·cm⁻⁵ = 3.0 Wood Units
• 400 dynes·sec·cm⁻⁵ = 5.0 Wood Units
• 800 dynes·sec·cm⁻⁵ = 10.0 Wood Units
Factors Affecting PVR
Factors Increasing PVR
- • Hypoxemia (low PaO₂)
- • Acidemia (low pH)
- • Hypercapnia (high PaCO₂)
- • Pulmonary embolism
- • Atelectasis
- • Vasoconstrictor drugs
Factors Decreasing PVR
- • Alkalemia (high pH)
- • Hypocapnia (low PaCO₂)
- • Exercise
- • Vasodilator drugs
- • Nitric oxide
Clinical Pearls 💎
PH Definition
Pulmonary hypertension is defined as MPAP ≥ 20 mmHg (2022 ESC/ERS guidelines)
Pre-capillary PH
PCWP ≤ 15 mmHg + PVR > 2 WU suggests pre-capillary pulmonary hypertension
Post-capillary PH
PCWP > 15 mmHg suggests post-capillary (left heart) pulmonary hypertension
TPG Significance
TPG > 12 mmHg suggests a significant transpulmonary gradient
Clinical Applications
Right Heart Function
Elevated PVR increases right ventricular afterload
PH Diagnosis
Essential for classifying pulmonary hypertension types
Treatment Monitoring
Tracks response to vasodilator therapy
Surgical Planning
Risk stratification for cardiac surgery
WHO Pulmonary Hypertension Classification
Group 1: Pulmonary Arterial Hypertension (PAH)
- • Idiopathic PAH
- • Heritable PAH
- • Drug/toxin induced
- • Associated with CTD, CHD, HIV
Hemodynamics: High PVR, normal PCWP
Group 2: Left Heart Disease
- • HFrEF / HFpEF
- • Valvular disease
- • Congenital cardiomyopathy
Hemodynamics: Variable PVR, elevated PCWP
Group 3: Lung Disease / Hypoxia
- • COPD
- • Interstitial lung disease
- • Sleep apnea
- • Chronic high altitude
Hemodynamics: Mildly elevated PVR
Group 4: CTEPH
- • Chronic thromboembolic PH
- • Other pulmonary obstruction
Hemodynamics: Very high PVR
Group 5: Unclear / Multifactorial
- • Hematologic disorders (sickle cell, myeloproliferative)
- • Systemic disorders (sarcoidosis, vasculitis)
- • Metabolic disorders (thyroid, glycogen storage disease)
Hemodynamics: Variable presentation
Understanding Pulmonary Vascular Resistance (PVR)
What is PVR?
Pulmonary Vascular Resistance (PVR) measures the resistance to blood flow through the pulmonary circulation. It quantifies the afterload faced by the right ventricle and helps assess the severity of pulmonary hypertension.
Key Measurements
- •MPAP: Obtained via right heart catheterization
- •PCWP/LAP: Reflects left atrial filling pressure
- •CO: Measured by thermodilution or Fick method
- •TPG: Pressure drop across pulmonary circulation
Clinical Significance
PVR > 3 Wood Units (240 dynes·sec·cm⁻⁵) is a key criterion for diagnosing pre-capillary pulmonary hypertension. Serial PVR measurements help monitor disease progression and treatment response.
Formula Explanation
PVR = 80 × (MPAP - LAP) / CO
or
PVR (WU) = (MPAP - LAP) / CO
Parameter Definitions
- PVR: Pulmonary Vascular Resistance
- MPAP: Mean Pulmonary Arterial Pressure (mmHg)
- LAP/PCWP: Left Atrial / Wedge Pressure (mmHg)
- CO: Cardiac Output (L/min)
- 80: Conversion factor to dynes·sec·cm⁻⁵
- WU: Wood Units (mmHg·min/L)
⚠️ Important Notes
- • PVR should be measured at rest
- • Accurate CO measurement is critical
- • PCWP often used as LAP surrogate
- • Consider indexed values (PVRi) in extreme body sizes
Medical Disclaimer
This PVR calculator is intended for educational and informational purposes only. It should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult qualified healthcare providers before making any healthcare decisions. The accuracy of this calculator depends on the correct input of hemodynamic measurements obtained through proper clinical procedures. Clinical interpretation should always be performed by qualified medical professionals in the context of the patient's overall clinical picture.
Comprehensive PVR Interpretation Guide
| Category | PVR (dynes·sec·cm⁻⁵) | Wood Units | Clinical Significance | Management |
|---|---|---|---|---|
| Low | < 120 | < 1.5 | Vasodilation, sepsis, or high CO states | Treat underlying cause |
| Normal | 120-240 | 1.5-3.0 | Normal pulmonary circulation | No intervention needed |
| Borderline | 240-320 | 3.0-4.0 | Early PH or exercise-induced | Close monitoring, risk factor modification |
| Mild PH | 320-480 | 4.0-6.0 | Mild pulmonary hypertension | Evaluate for specific PH therapy |
| Moderate PH | 480-800 | 6.0-10.0 | Moderate pulmonary hypertension | Targeted PH therapy recommended |
| Severe PH | > 800 | > 10.0 | Severe pulmonary hypertension | Aggressive therapy, consider transplant evaluation |
Treatment Implications Based on PVR
Pharmacological Therapy
Vasodilators
PDE-5 inhibitors, prostacyclins, ERAs for elevated PVR
Diuretics
Reduce preload in post-capillary PH
Oxygen Therapy
Prevents hypoxic pulmonary vasoconstriction
Advanced Interventions
Pulmonary Endarterectomy
For CTEPH (Group 4) with accessible clots
Balloon Atrial Septostomy
Palliative for severe PAH with right heart failure
Transplantation
Heart-lung or lung transplant for refractory disease
🎯 Treatment Goals
- • Target: PVR < 240 dynes·sec·cm⁻⁵ (< 3 WU) with therapy
- • Reduce right ventricular afterload and prevent RV failure
- • Improve exercise capacity and quality of life
- • Prevent disease progression and reduce mortality
Frequently Asked Questions (FAQ)
What is a normal PVR value?
Normal pulmonary vascular resistance (PVR) is typically less than 240 dynes·sec·cm⁻⁵ or less than 3.0 Wood Units. Values between 120-240 dynes·sec·cm⁻⁵ (1.5-3.0 WU) are considered within the normal range.
Normal Range: 120-240 dynes·sec·cm⁻⁵ (1.5-3.0 Wood Units)
What does elevated PVR indicate?
Elevated PVR (above 240 dynes·sec·cm⁻⁵ or 3.0 WU) indicates increased resistance to blood flow through the pulmonary circulation, which is a key diagnostic criterion for pulmonary hypertension. This means the right ventricle must work harder to pump blood through the lungs.
- • Borderline (240-320): Early PH or exercise-induced
- • Mild PH (320-480): Requires further evaluation
- • Moderate PH (480-800): Needs targeted therapy
- • Severe PH (>800): Critical condition requiring aggressive treatment
What is the difference between PVR and Wood Units?
PVR can be expressed in two different units:
- • dynes·sec·cm⁻⁵: The standard SI unit derived from pressure, flow, and conversion factor (80)
- • Wood Units (WU): A simpler unit where 1 WU = 80 dynes·sec·cm⁻⁵
Conversion: To convert dynes·sec·cm⁻⁵ to Wood Units, divide by 80. Example: 240 dynes·sec·cm⁻⁵ = 3.0 Wood Units
How is PVR measured?
PVR is calculated using measurements obtained during right heart catheterization:
- • MPAP (Mean Pulmonary Arterial Pressure): Measured directly with a catheter in the pulmonary artery
- • PCWP/LAP (Wedge Pressure): Measured by advancing the catheter until it "wedges" in a small pulmonary vessel
- • Cardiac Output: Measured using thermodilution or Fick method
The formula PVR = 80 × (MPAP - LAP) / CO is then applied to calculate resistance.
What is the Transpulmonary Gradient (TPG)?
The Transpulmonary Gradient (TPG) is the pressure difference across the pulmonary circulation, calculated as MPAP - LAP (or PCWP). It represents the driving pressure for blood flow through the lungs.
Interpretation:
• Normal: < 12 mmHg
• Elevated: 12-25 mmHg
• Severely elevated: > 25 mmHg
TPG helps distinguish between pre-capillary and post-capillary pulmonary hypertension.
What is the difference between pre-capillary and post-capillary pulmonary hypertension?
These classifications help identify the underlying cause of pulmonary hypertension:
Pre-capillary PH
- • PCWP ≤ 15 mmHg
- • PVR > 2 Wood Units
- • Causes: PAH, CTEPH, lung disease
- • WHO Groups 1, 3, 4, 5
Post-capillary PH
- • PCWP > 15 mmHg
- • Variable PVR
- • Causes: Left heart disease
- • WHO Group 2
When should PVR be indexed to body surface area?
Indexed PVR (PVRi) should be considered in:
- • Pediatric patients (to account for body size differences)
- • Very small or very large adult patients
- • When comparing serial measurements during growth
- • Congenital heart disease evaluation
PVRi is calculated by multiplying PVR by body surface area (BSA): PVRi = PVR × BSA
What factors can affect PVR measurements?
Factors that increase PVR:
- • Hypoxemia (low oxygen)
- • Acidemia (low pH)
- • Hypercapnia (high CO₂)
- • Pulmonary embolism
- • Atelectasis
- • Vasoconstrictor medications
- • Cold temperature
Factors that decrease PVR:
- • Alkalemia (high pH)
- • Hypocapnia (low CO₂)
- • Supplemental oxygen
- • Exercise
- • Vasodilator medications
- • Nitric oxide
- • Warm temperature
Can PVR be estimated without cardiac catheterization?
While echocardiography can estimate pulmonary artery pressures non-invasively, accurate PVR measurement requires right heart catheterization. Echocardiography can suggest the presence of pulmonary hypertension but cannot definitively calculate PVR or classify the type of PH.
Important: Right heart catheterization remains the gold standard for diagnosing pulmonary hypertension and measuring PVR accurately.
What are the treatment options for elevated PVR?
Treatment depends on the underlying cause and severity of elevated PVR:
- • Lifestyle modifications: Avoid high altitude, maintain healthy weight, supervised exercise
- • Oxygen therapy: For hypoxemia to prevent further vasoconstriction
- • Medications: PDE-5 inhibitors, prostacyclins, endothelin receptor antagonists
- • Diuretics: To reduce fluid overload and preload
- • Anticoagulation: In selected cases like CTEPH
- • Surgical interventions: Pulmonary endarterectomy for CTEPH
- • Transplantation: Heart-lung or lung transplant for refractory cases
What is the prognosis with elevated PVR?
Prognosis depends on several factors including:
- • Severity of PVR elevation
- • Underlying cause (WHO classification group)
- • Right ventricular function
- • Response to therapy
- • Presence of comorbidities
With modern therapies, many patients with pulmonary hypertension can achieve improved symptoms and quality of life. Early diagnosis and treatment are crucial for better outcomes.
How often should PVR be monitored?
Monitoring frequency depends on the clinical situation:
- • At diagnosis: Baseline measurement via right heart catheterization
- • After starting therapy: Repeat catheterization at 3-6 months to assess response
- • Stable patients: Annual clinical assessment with echocardiography
- • Worsening symptoms: Repeat catheterization to guide treatment adjustment
- • Before major surgery: To assess perioperative risk
Note: Serial measurements help track disease progression and treatment effectiveness. Your healthcare team will determine the appropriate monitoring schedule based on your individual situation.